Process for forming a solid fuel composition from mixed solid waste

ABSTRACT

Systems and methods of producing a solid fuel composition are disclosed. In particular, systems and methods for producing a solid fuel composition by heating and mixing a solid waste mixture below atmospheric pressure to a maximum temperature sufficient to melt the mixed plastics within the solid waste mixture is disclosed.

CROSS-REFERENCE

This application is a continuation application of U.S. patentapplication Ser. No. 14/929,086, filed on Oct. 30, 2015, which claimsthe benefit of the filing date under 35 U.S.C. § 119 to U.S. ProvisionalPatent Application Ser. No. 62/072,822 filed Oct. 30, 2014, and entitled“Process for Forming a Solid Block Composition From Mixed Solid Waste,”the disclosure of which is herein incorporated by reference in itsentirety for all purposes.

TECHNICAL FIELD

The present disclosure relates to methods of processing mixed solidwastes. More specifically, the present disclosure relates to methods forproducing a solid fuel composition from a solid waste mixture,especially without the formation of syngas.

BACKGROUND

The management of solid wastes such as municipal wastes fromresidential, institutional, and commercial sources, agricultural wastes,and other wastes such as sewage sludge, remains a challenging issue withever-evolving solutions. As landfills reach and exceed capacityworldwide, and as the solid waste industry and societies generally limitthe use of landfills, alternative methods of managing solid wastes andhave been developed that additionally process the solid wastes to reducethe volume introduced into landfills. Recycling of metals, plastics, andpaper products, as well as composting organic matter are relativelycommon methods of reducing the overall volume of solid wastes going tolandfills. Waste-to-Energy processes have also been developed to convertthe energetic content of solid wastes into a more usable form such aselectrical power.

A variety of Waste-to-Energy processes may use thermal treatments suchas incineration, pyrolysis, or gasification to release the energycontent of the solid waste stream, which is subsequently used to drivedownstream electrical generators. Although pyrolysis and gasificationafford many advantages over incineration in Waste-to-Energy processes,the effective use of pyrolysis or gasification is limited when municipalsolid waste (MSW) or agricultural waste is used as the feedstock, due tothe high water content, low density, and lack of homogeneity.

Efficient operation of a pyrolysis or a gasification chamber typicallyuses feedstock that is high density and of consistent composition withessentially no moisture. Because solid waste streams are inherently lowdensity and variable in composition, most Waste-to-Energy plantsincinerate the solid waste stream to liberate the energy of the solidwaste stream. Enhanced pyrolysis mechanisms, such as advancedgasification, may overcome inefficiencies associated with the inherentinconsistency of solid waste composition, but these advanced mechanismsrequire significant investment in specialized equipment. Further, theyare still limited by the quality of the feedstock.

Other processes use pelletizers to render the solid waste stream of thepyrolysis chamber more uniform in size. But the pelletized solid wasteretains the variation in composition inherent in solid waste streams.Further, pelletizing the solid waste stream fails to transform the solidwaste into a high density and low moisture fuel appropriate for theefficient operation of a pyrolysis (or gasification) chamber.

A need exists for a solid fuel composition and a process of producing asolid fuel composition from a solid waste stream that may include mixedsolid wastes and other wastes to be used as a feedstock. Such a fuelwould provide efficient operation of a pyrolysis (or gasification)chamber as part of a Waste-to-Energy process, without additional capitalinvestment in advanced machinery. In addition, a need exists for aprocess that transforms a solid waste stream with variable compositioninto a solid fuel composition with a relatively consistent compositionthat is high density and low moisture, as this provides a better fuelcomposition. Further, a need exists for a process for forming a solidfuel composition from a solid waste stream that may further eliminateodors, bacteria, and other undesired properties of the solid wastestream used to produce the solid fuel composition. The solid fuelcomposition resulting from such a process may enable the use ofhigh-efficiency pyrolysis or gasification methods as part of aWaste-to-Energy process by providing a homogenized, dry, dense, andenergy rich fuel primed for pyrolysis or gasification.

BRIEF SUMMARY

The methods disclosed herein process solid waste mixtures withoutextensive presorting or predrying, as typically employed for producingan engineered fuel. Because the source material need not be dried orpresorted (other than the optional removal non-combustibles of metal,glass, and hazardous materials), variations of content based on the siteof origin, the season, or the weather do not substantially affect theprocess.

The process starts by obtaining a solid waste mixture which includesorganic material, trash, and plastic. The system processes the solidwaste mixture in a process vessel below atmospheric pressure, drivingaway excess moisture, volatile organic compounds (VOCs), chlorinatedorganics, and chlorine gas, which are sequestered without exposure ofthese gasses to the atmosphere. Then heat increases after removal of thewater and VOCs to melt mixed plastics in the solid waste mixture. Thisprocess melts plastics content within the dried solid waste mixture,thereby distributing the plastic throughout the solid fuel compositionand increasing the density of the solid fuel composition, in contrast toexisting compositions. The finished product has not been pyrolyzed andincludes organic compounds and plastic. The finished product is of ageneral uniform consistency, meaning that large pieces within the solidwaste mixture are reduced to an average particle size equal to or lessthan other individual pieces within the solid waste mixture. Thefinished product also has low water content (<1% wt.), and is suitablefor a variety of post process applications, including use as fuel forincineration, or as syngas feedstock, for example via pyrolysis orgasification.

Briefly, therefore the present disclosure encompasses a method forproducing a solid fuel composition without syngas formation with anenergy content of at least 8,000 BTU/lb. from a solid waste mixture. Themethod includes heating a solid waste mixture that includes at least 5%wt. mixed plastics within a process vessel to a temperature no greaterthan 110° C. (such as about 100° C., or between about 90° C. and about110° C.) to separate the solid waste mixture into a dried solid wastemixture and vaporized compounds released from the heated solid wastemixture.

The vaporized compounds may include any one or more of water vapor, atleast one volatile organic compound, chlorinated organic compound,chlorine gas, and any combination thereof. The method may also includeremoving the vaporized compounds from the process vessel by reducing thepressure within the process vessel to less than about 50 torr using avacuum system attached at the vacuum port; heating and mixing the driedsolid waste mixture to a maximum temperature of at least 160° C. to forma heated solid waste mixture comprising melted mixed plastics; extrudingthe heated solid waste mixture from the process vessel using theextrusion outlet; and cooling the extruded mixture to less than about65° C. to form the solid fuel composition. The solid waste mixture mayinclude from about 20% wt. to about 40% wt. mixed plastics.Alternatively, the solid waste mixture may include from about 5% wt. toabout 35% wt. mixed plastics.

The solid waste mixture comprises municipal solid waste and agriculturalwaste. The method may further comprise analyzing the solid waste mixturefor non-combustible solid waste and, if present, removing thenon-combustible solid waste. Ultimately, the feedstock must besubstantially free of non-combustible metallic wastes. The method mayfurther comprise analyzing the solid waste mixture for a mixed plasticscontent and, if necessary, adjusting the amount of mixed plastics in thesolid waste mixture to between about 5% wt. an about 60% wt.

The mixed plastics may comprise one or more plastics selected from thegroup consisting of polyester, polyethylene terephthalate, polyethylene,polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene,polyamides, acrylonitrile butadiene styrene, polyethylene/acrylonitrilebutadiene styrene, polycarbonate, polycarbonate/acrylonitrile butadienestyrene, polyurethanes, maleimide/bismaleimide, melamine formaldehyde,phenol formaldehydes, polyepoxide, polyetheretherketone, polyetherimide,polyimide, polylactic acid, polymethyl methacrylate,polytetrafluoroethylene, and urea-formaldehyde. In particular, the mixedplastics may comprise polyvinyl chloride, polyvinylidene chloride, andcombinations thereof, and the dried solid waste is heated to at leastabout 190° C.

More specifically, the solid waste mixture may include from about 20%wt. to about 40% wt. mixed plastics. Alternatively, the solid wastemixture may include from about 5% wt. to about 35% wt. mixed plastics.The resultant solid fuel composition may be a hydrophobic, stable, andnon-biodegradable material. The material may include from about 40% wt.to about 80% wt. carbon; from about 5% wt. to about 20% wt. hydrogen;from about % wt. to about 20% wt. oxygen; less than about 2% wt. sulfur;less than about 2% wt. chlorine; and less than about 1% wt. water. Theresultant solid fuel composition may have an energy content of at least8,000 BTU/lb. The resultant solid fuel composition may be substantiallyfree of volatile organic compounds.

The process vessel may include one or more heated walls maintained at awall temperature of at least about 190° C., a mixer in the interiorvolume of the process vessel and operatively connected to the processvessel, an extruding element passing through a first opening in theprocess vessel, and a vacuum port passing through a second opening inthe process vessel; wherein the process vessel is attached via thevacuum port to a vacuum system comprising a vacuum pump. Typically, thevaporized compounds include any of the following: water vapor, volatileorganic compounds, chlorinated organic compounds, chlorine gas, and anycombination thereof.

The method may further include shredding the solid waste mixture intopieces with a maximum dimension or diameter of about two inches prior tointroducing the solid waste mixture into the process vessel. The methodmay further include condensing the vaporized compounds removed from theprocess vessel to produce wastewater comprising one or more selectedfrom the group consisting of at least one volatile organic compound,chlorinated organic compounds, chlorine gas, and any combination thereofdissolved in a condensed water vapor. The method may further includeremoving the one or more volatile organic compounds, chlorinated organiccompounds, chlorine gas, and any combination thereof from the wastewaterto produce treated wastewater. Chlorine gas, chlorinated organiccompounds, and volatile organic compounds are environmental pollutantssubject to government regulation. Trapping and removing these compoundsvia the wastewater reduces the volume of these compounds, which wouldotherwise escape into the atmosphere.

The wall temperature may be maintained from about 190° C. to about 280°C. and the maximum temperature of the solid waste mixture may range fromabout 160° C. to about 250° C. to separate the dried solid waste mixturefrom the vaporized compounds. Preferably the wall temperature ismaintained at about 280° C. and the solid waste mixture is heated toabout 250° C. to soften and disperse the mixed plastics within theheated solid waste mixture. The method may further include monitoringthe wall temperature of the one or more heated walls and using themonitored wall temperature to modulate operation of a heater operativelycoupled to the one or more heated walls to automatically maintain theone or more heated walls at a desired wall temperature. The method mayfurther include monitoring a headspace pressure within a headspacevolume within the process vessel and using the monitored headspacepressure to modulate operation of the vacuum system to automaticallymaintain the reduced pressure within the process vessel.

The method may further include monitoring moisture content within thevaporized compounds removed from the process vessel. An initial increasein the moisture content may indicate that the solid waste mixture issufficiently heated to release water vapor and a subsequent decrease toa stable minimum moisture level may indicate that the solid wastemixture may include less than about 2% wt. water, such as less thanabout 1% wt. water.

The method may further include monitoring the mixture temperature withinthe solid waste mixture within the process vessel. Typically, themonitored mixture temperature equal to the predetermined temperature mayindicate that the solid waste mixture is ready for extrusion from theprocess vessel. The method may further include monitoring a weight ofthe solid waste mixture within the process vessel. A decrease in themonitored weight to a minimum weight may indicate that the vaporizedcompounds may be fully removed from the solid waste mixture. The solidwaste mixture may be heated and mixed for a predetermined durationranging from about 0.5 hours to about 2 hours. The method may furtherinclude cutting the extruded mixture into pieces during cooling.

While multiple embodiments are disclosed, still other embodiments of thepresent disclosure will become apparent to those skilled in the art fromthe following detailed description, which shows and describesillustrative embodiments of the disclosure. As will be realized, theinvention is capable of modifications in various aspects, all withoutdeparting from the spirit and scope of the present disclosure.Accordingly, the drawings and detailed description are to be regarded asillustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures illustrate various aspects of the disclosure.

FIG. 1 is a flowchart illustrating a method of producing a solid fuelcomposition from a solid waste mixture.

FIG. 2 is a graph schematically illustrating a temperature profile andassociated processes within a solid waste mixture during a process ofproducing a solid fuel composition from the solid waste mixture.

FIG. 3 is a flowchart illustrating a method of removing vaporizedcompounds from a heated solid waste mixture.

FIG. 4 is a block diagram of a system for producing a solid fuelcomposition from a solid waste mixture.

FIG. 5 is a cross-sectional view of an extruder outlet 434.

FIG. 6 is a schematic diagram of a dual-chamber process vessel.

FIG. 7 is a schematic of a system as disclosed herein.

Corresponding reference characters and labels indicate correspondingelements among the views of the drawings. The headings used in thefigures should not be interpreted to limit the scope of the claims.

DETAILED DESCRIPTION

The present disclosure encompasses methods and systems for producing asolid fuel composition without syngas formation with an energy contentof at least 8,000 BTU/lb. Systems and methods for forming a solid fuelcomposition from a solid waste mixture that may include at least about5% wt. plastics are provided herein below. The solid fuel compositionmay be formed by heating the solid waste mixture within a process vesselto a temperature of at least about 100° C. to separate the solid wastemixture into a dried solid waste mixture and vaporized compoundsincluding, but not limited to, water vapor. The vaporized compounds maythen be removed from the process vessel using an attached vacuum system,and the remaining dried solid waste mixture may then be mixed and heatedto a maximum temperature of up to about 250° C. At the maximumtemperature, any plastics within the solid waste mixture may be meltedand distributed throughout the mixture. The heated solid waste mixturemay then be extruded below about 200° C. and cooled to form the solidfuel mixture.

The resulting solid fuel mixture may have energy content of at least8,000 BTU/lb. and a density of at least about 30 lb./ft³. The solid fuelmixture may also be sterilized due to the high maximum temperaturewithin the process vessel, and hydrophobic and non-porous by virtue ofthe plastics distributed throughout the solid fuel composition. As aresult, the solid fuel mixture may be stored for extended periods at awide variety of storage conditions without risk of biodegrading orotherwise altering the composition.

Detailed descriptions of method and systems for the solid fuelcomposition, as well as a description of the solid fuel compositionitself, are provided herein below.

I. Method of Forming Solid Fuel Composition

A method for forming a solid fuel composition from a solid waste mixtureis disclosed that includes heating and mechanically agitating a solidwaste mixture within a process vessel to mix and homogenize theindividual components of the solid waste. In addition, any vaporizedcompounds released by the heated solid waste mixture may be removedusing a vacuum within the process vessel (i.e., at a pressure belowatmospheric). The resulting contents of the process vessel may beextruded, formed into a desired shape, and cooled to form the solid fuelcomposition.

The method overcomes many of the limitations of previous Waste-to-Energymethods by transforming a solid waste mixture, which may be variable incomposition, to a solid fuel composition with relatively low compositionvariability. In addition, the solid fuel composition produced by themethod is essentially sterile and non-porous, enabling the solid fuelcomposition to be transported and stored for prolonged periods withoutneed for specialized equipment or facilities. In addition, the solidfuel compositions are compatible with various pyrolysis processesassociated with higher-yield Waste-to-Energy methods.

Some Waste-to-Energy processes incinerate the solid wastes, definedherein as burning the solid wastes in the presence of oxygen, therebygenerating heat to produce steam that drives downstream steamgenerators. However, the incineration process also produces potentiallyharmful emissions that must either be scrubbed from the incinerator'sexhaust stream or released to the environment. On the other hand, thepresent disclosure provides a solid fuel composition which has alreadyhad VOCs, chlorinated organic compounds, and chlorine gas removed, sothat when the solid fuel composition incinerated or combusted, it doesnot emit these harmful pollutants into the environment and the exhauststream need not be scrubbed for these compounds.

Other Waste-to-Energy processes use pyrolysis, which is thesuper-heating of the volatile components of an organic substance,created by heating the substance at a temperature ranging from about400° F. to about 1,400° F. (about 205° C. to about 760° C.) in anoxygen-starved environment. Pyrolysis is a type of thermolysis,resulting in the irreversible thermochemical decomposition of organicmaterial. Pyrolysis involves a simultaneous change of chemicalcomposition and physical phase, where the feedstock is divided into ash,char (such as biochar), synoil (biooil), and syngas (biogas). Pyrolysisdiffers from combustion (oxidation), where the fuel reacts with oxygen,and hydrolysis, where the fuel reacts with water. The syngas and/orother fluids generated from pyrolysis enable the downstream efficientgenerators for power production, as opposed to the less efficient steamgenerators used in conjunction with incineration. The present disclosureprovides a solid fuel composition that is not pyrolyzed, meaning that ithas not been divided into ash, char, synoil, and syngas. Rather, thepresent solid fuel composition is a homogenized, dry, dense, and energyrich fuel primed for pyrolysis.

Gasification is similar to pyrolysis in that it involves heating organicsubstances in even higher temperature environments of about 900° F. toabout 3,000° F. (about 480° C. to about 1,650° C.) with little to nooxygen. Gasification has the advantage of creating a greater amount ofsyngas, as some of the nonvolatile carbon char left from pyrolysis mayalso be converted to syngas via gasification. The present disclosureprovides a solid fuel composition that is gasified, but which is ahomogenized, dry, dense, and energy rich fuel primed for gasification.

The solid fuel composition disclosed herein can be used in any of theabove process. The present solid waste mixture is chemically andphysically transformed to provide a solid fuel composition especiallysuitable for pyrolysis, gasification and/or incineration. Withoutwishing to be bound by theory, pyrolysis typically cannot occur until asubstantial portion of moisture is removed from the feedstock. The solidfuel compositions disclosed herein have a very low water content and canbe immediately pyrolyzed. The solid fuel compositions have beenprocessed to remove VOCs, chlorinated organic compounds, and chlorinegas. Generally, non-combustible waste materials have also been removed.The solid waste mixture is processed to the point just before pyrolysisoccurs, in which the reaction is stopped by densifying and cooling thefeedstock, thus keeping the gas than can be burned “locked” into thesolid fuel composition. The resulting solid fuel composition primed forpyrolysis and related processes.

Blending of Solid Waste Mixture

FIG. 1 is a flowchart illustrating a method 100 to form a solid fuelcomposition from a solid waste mixture. Depending on the solid wastemixture subjected to the method 100, the solid waste mixture mayoptionally be formed by blending a sorted solid waste with mixedplastics at step 101. The feedstock for the process may be a solid wastemixture that includes at least about 20% wt. plastics. The feedstock forthe process may be a solid waste mixture that includes at least about 5%wt. plastics.

“Waste” generally refers to carbon-containing combustible material thathas been discarded after its primary use, including solid waste.Generally, the waste may be wet and heterogeneous, containing a portionof non-combustible waste. “Solid waste” refers to any garbage or refuse,sludge from a wastewater treatment plant, water supply treatment plant,or air pollution control facility and other discarded material,including solid, liquid, semi-solid, or contained gaseous materialresulting from industrial, commercial, mining, and agriculturaloperations, and from community activities.

A variety of sources of solid waste can be used. The solid waste mixturemay be derived from non-hazardous waste sources including, but notlimited to, municipal waste, agricultural waste, sewage sludge,household waste, discarded secondary materials, and industrial solidwaste. “Municipal waste,” or “municipal solid waste” (MSVV), as usedherein, may refer to any household waste or commercial solid waste orindustrial solid waste. Non-limiting examples of wastes that may beincluded in the solid waste mixture include biodegradable waste such asfood and kitchen waste; green wastes such as lawn or hedge trimmings;paper; mixed plastics; solid food waste; solid agricultural waste;sewage sludge; and automotive shredder residue.

“Household waste” or “residential waste” refers to any solid waste(including garbage, trash, and sanitary waste in septic tanks) derivedfrom households (including single and multiple residences, hotels andmotels, bunkhouses, ranger stations, crew quarters, campgrounds, picnicgrounds, and day-use recreation areas).

“Commercial solid waste” refers to all types of solid waste generated bystores, offices, restaurants, warehouses, and other nonmanufacturingactivities, excluding residential and industrial wastes.

“Industrial solid waste” refers to non-hazardous solid waste generatedby manufacture or industrial processes. Examples of industrial solidwaste include, but are not limited to, waste resulting from thefollowing manufacturing processes: Electric power generation;fertilizer/agricultural chemicals; food and relatedproducts/by-products; leather and leather products; organic chemicals;plastics and resins manufacturing; pulp and paper industry; rubber andmiscellaneous plastic products; textile manufacturing; transportationequipment; and water treatment. This term does not include mining wasteor oil and gas waste.

The solid waste mixture may comprise discarded non-hazardous secondarymaterial, in which case solid fuel compositions produced from thosesolid waste mixtures may be legally categorized as “non-waste.”“Secondary material” refers to any material that is not the primaryproduct of a manufacturing or commercial process, and can includepost-consumer material, off-specification commercial chemical productsor manufacturing chemical intermediates, post-industrial material, andscrap. Examples of non-hazardous secondary materials include scrap tiresthat are not discarded and are managed by an established tire collectionprogram, including tires removed from vehicles and off-specificationtires; resinated wood; coal refuse that has been recovered from legacypiles and processed in the same manner as currently-generated coalrefuse; and dewatered pulp and paper sludges that are not discarded andare generated and burned on-site by pulp and paper mills that burn asignificant portion of such materials where such dewatered residuals aremanaged in a manner that preserves the meaningful heating value of thematerials.

“Resinated wood” refers to wood products (containing binders andadhesives) produced by primary and secondary wood productsmanufacturing. Resinated wood includes residues from the manufacture anduse of resinated wood, including materials such as board trim, sanderdust, panel trim, and off-specification resinated wood products that donot meet a manufacturing quality or standard.

“Mixed plastics” refer to any combination of synthetic or semi-syntheticorganics that are malleable can be molded into solid objects of diverseshapes, and which are typically found in municipal solid waste. Suitableexamples of mixed plastics include, but are not limited to, polyester(PES), polyethylene terephthalate (PET), polyethylene (PE), high-densitypolyethylene (HDPE), polyvinyl chloride (PVC), polyvinylidene chloride(PVDC, Saran™), low-density polyethylene (LDPE), polypropylene (PP),polystyrene (PS), polyamides (PA) (Nylons), acrylonitrile butadienestyrene (ABS), polyethylene/acrylonitrile butadiene styrene (PE/ABS),polycarbonate (PC), polycarbonate/acrylonitrile butadiene styrene(PC/ABS), polyurethanes (PU), maleimide/bismaleimide, melamineformaldehyde (MF), phenol formaldehydes (PF), polyepoxide (Epoxy),polyetheretherketone (PEEK), polyetherimide (PEI, Ultem™), polyimide,polylactic acid (PLA), polymethyl methacrylate (PMMA, acrylic),polytetrafluoroethylene (PTFE), urea-formaldehyde (UF), and combinationsthereof.

The mixed plastics may comprise one or more plastics selected from thegroup consisting of polyester, polyethylene terephthalate, polyethylene,polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene,polyamides, acrylonitrile butadiene styrene, polyethylene/acrylonitrilebutadiene styrene, polycarbonate, polycarbonate/acrylonitrile butadienestyrene, polyurethanes, maleimide/bismaleimide, melamine formaldehyde,phenol formaldehydes, polyepoxide, polyetheretherketone, polyetherimide,polyimide, polylactic acid, polymethyl methacrylate,polytetrafluoroethylene, urea-formaldehyde, and combinations thereof.

The mixed plastics may comprise one or more plastics selected from thegroup consisting of polyester, polyethylene terephthalate, polyethylene,polyvinyl chloride, polyvinylidene chloride, polypropylene, polystyrene,polyamides, polycarbonate, polyurethanes, and combinations thereof. Themixed plastics may comprise polyethylene.

The mixed plastics may comprise polyvinyl chloride, polyvinylidenechloride, and combinations thereof, and the dried solid waste may beheated to at least about 190° C.

The solid waste mixture may be analyzed to detect non-combustible solidwaste. Based on the analysis, a municipal solid waste stream may belightly sorted to remove plastics, and to further exclude inert wastesincluding, but not limited to, glasses, metals, concrete, bricks, andany other inert material, resulting in a sorted solid waste. Inertmaterial, as used herein, refers to any material not likely to releaseenergy when subjected to a combustion or pyrolysis process. The plasticsremoved from the municipal solid waste stream may be retained and mixedwith the sorted solid waste to form the solid waste mixture from whichthe solid fuel composition is formed. The non-combustible waste maycomprise non-combustible metallic waste, including for example scrapmetal and metals chunks. The non-combustible metallic waste may compriseferrous metal, such as iron, steel, and other iron-containing alloys,and non-ferrous metal, which are metals and alloys which do not containan appreciable amount of iron.

The solid waste mixture may be analyzed to determine the amount of mixedplastics present therein. The amount of mixed plastics present in thesolid waste can and will vary. The solid waste mixture used as afeedstock to the process described herein may be formed by mixing sortedsolid waste and plastics in a predetermined ratio based on the analysis.The mixed plastics are those typically found in the solid waste stream(e.g., MSVV), used without further ratio adjustment (that is, sortingand remixing). The amount of mixed plastics affects the fuelcompositions produced in the methods and systems described herein, andmay be selected based on the economic model and/or on aproject-by-project basis.

The solid waste mixture may include at least about 20% wt. mixedplastics. The solid waste mixture may include from about 20% wt. toabout 60% wt. mixed plastics. The solid waste mixture may include fromabout 20% wt. to about 40% wt. mixed plastics. The feedstock for theprocess may include between about 5% wt. to about 35% wt. mixedplastics. The feedstock for the process may include between about 5% wt.to about 30% wt. mixed plastics. The feedstock for the process includesgreater than about 5% wt. plastics.

The plastics may help bind together the solid fuel mixture resultingfrom the methods as described herein, and may further reduce theporosity and water activity of the solid fuel composition. In addition,the plastics in the solid fuel composition may influence the type ofproducts resulting from pyrolysis processes using the solid fuelcomposition as a feedstock. Without being limited to any particulartheory, solid fuel mixtures with a higher proportion of plastics arethought to produce higher yields of synoil using pyrolysis processes.Solid fuel mixtures with a lower proportion of plastics and a higherproportion of paper and cardboard are thought to produce higher yieldsof syngas using pyrolysis processes.

The solid waste mixture may have a highly variable composition due tothe variable nature of municipal solid waste streams. A municipal solidwaste stream may vary in composition due to a variety of factorsincluding, but not limited to, different seasons, different locationswithin a country (urban versus rural), and/or different countries(industrial versus emerging).

The water contained within the solid waste mixture containing the sortedsolid waste and the mixed plastics may vary and may influence the timeand/or maximum temperature needed to remove the water from the solidwaste mixture during the formation of the solid fuel composition usingthe methods described herein. To dry, a period of time may be selectedthat is sufficient to remove the water from the solid waste.

For example, the mixed solid waste may contain a variable amount ofwater ranging from about 10% wt. to about 60% wt. Specifically, themixed solid waste may contain an amount of water ranging from betweenabout 10% wt. and about 20% wt., the mixed solid waste may contain atleast 10% wt. water, at least 20% wt. water, at least 30% wt. water, atleast 40% wt. water, and at least 50% wt. water.

The available plastics may similarly vary. To form a mixture, the solidwaste and the plastics may be individually weighed prior to mixing toensure that the solid waste mixture is formed at the predeterminedweight ratio of solid waste and plastics. The solid waste and plasticsmay each be transferred from a storage area to a mixing area usingweighing devices including, but not limited to, a weighing conveyor thatweighs the solid waste and plastics as they are combined to form thesolid waste mixture. The plastics within the solid waste mixture mayinclude plastics removed from the municipal waste stream during sorting,plastics obtained from outside sources, and any combination thereof.

Shredding of Solid Waste Mixture

Next, the solid waste mixture may be shredded to reduce particles to anaverage particle size equal to or less than other individual pieceswithin the solid waste mixture. Referring again to FIG. 1 , the methodmay further include optionally shredding the solid waste mixture at step102. Any known shredding device may be used to shred the solid wastemixture without limitation including, but not limited to, a single-shaftindustrial shredder, a two-shaft industrial shredder, a three-shaftindustrial shredder, a four-shaft industrial shredder, a hammer mill, agrinder, a granulator, a chipper, and any other suitable device forreducing the size of individual pieces within the solid waste mixture.By shredding the solid waste mixture, the maximum dimensions and maximumdiameters of individual pieces within the solid waste mixture arereduced, thereby enhancing the blending of the individual components ofthe solid waste mixture during subsequent steps of the method 100,resulting in a more uniform composition within the solid fuel blocksproduced using the method 100.

The shredded solid waste mixture may include a plurality of pieces witha maximum dimension or a maximum diameter of less than about 4 inches.The plurality of pieces may have a maximum dimension or maximum diameterof less than 3.5 inches, less than 3 inches, less than 2.5 inches, lessthan 2 inches, less than 1.5 inches, and less than 1 inch, and less than0.5 inches. The maximum dimension may be less than about 2 inches.

Initial Heating of Solid Waste Mixture

Next the method includes introducing the solid waste mixture into aprocess vessel at step 104. The solid waste mixture may be introducedinto the process vessel using any known devices and methods withoutlimitation. The solid waste mixture may be introduced by opening aresealing hatch or other opening of the process vessel, inserting thesolid waste mixture, and closing and/or resealing the resealing hatch.The system may include a loading device including, but not limited to, ahopper to introduce the solid waste mixture into the process vessel asdescribed herein. The loading device may be operatively coupled to ashredding device or may incorporate a shredding device. The loadingdevice may include a mixer to blend the pieces within the solid wastemixture prior to introduction into the process vessel.

After entry in to the process vessel, the solid waste mixture is heatedto a temperature of about 100° C. at step 106, such as from about 90° C.to about 110° C. At this temperature, water and volatile organiccompounds within the solid waste mixture which have a boiling point ator below the boiling point of water are vaporized. The vaporizedcompounds include, but are not limited to, water, organic solvents, andother compounds may be vaporized within the solid waste mixture, therebyseparating the solid waste mixture into a dried solid waste andvaporized compounds. The vaporized compounds may primarily comprise orconsist essentially of water.

Without wishing to be bound by theory, proceeding directly tohigh-temperature processing without lower-temperature drying causes themixed plastics in the solid waste mixture to melt, thereby reducing thevoid space within the solid waste mixture and trapping water and VOCswithin the solid waste mixture. In addition, some low-melt plastics andplasticizers at higher temperatures may react with the residual water,which would interfere with the chemistry in later process steps.Instead, the solid waste mixture is first dried at a lower temperatures(e.g., between about 90° C. and about 110° C.) to evaporate water and towarm the nonaqueous content. After the water evaporates and is removedfrom the process vessel, the temperature is increased, allowing theplastics to melt within the low-moisture dried solid waste mixture.

The solid waste mixture may optionally be mixed as it is heated at step106. Without being limited to any particular theory, the mixing mayblend the individual components of the solid waste mixture into a moreconsistent composition and may also reduce voids or air pockets withinthe solid waste mixture. In addition, the mixing may enhance the heatexchange from the heated walls of the process vessel and the solid wastemixture within the vessel; the compression and shearing imparted to thesolid waste mixture by the mixing blades may further enhance heating.Further, the mixing may facilitate the release of steam and othervaporized compounds from the heated solid waste mixture.

The solid waste mixture may be mixed within the process vessel at amixing speed selected to impart shear stress to the solid waste mixturesufficient to mechanically break down pieces or chunks of solid wasteinto successively smaller pieces or chunks. The mixing speed may alsodepend upon any one or more of at least several additional factorsincluding, but not limited to, the type of mixer or mixing bladeprovided within the process vessel, and/or the mixing time.

The process vessel may be designed to provide a heated wall to transferheat into the solid waste mixture as it is mixed within the vessel asdescribed herein below. The heated wall may be maintained at atemperature essentially equal to a final temperature of the solid wastemixture. Such temperatures are suitable for converting the solid wastemixture into a solid fuel mixture. The at least one heated wall may bemaintained at a temperature at least about 30° C. or higher than thedesired final temperature of the solid waste mixture to accelerate theheating process.

The vaporized compounds released by the solid waste mixture duringheating at step 106 may be retained within the headspace of the processvessel to be removed in a subsequent step described herein below. Thevaporized compounds released by the solid waste mixture during heatingat step 106 may be continually removed from the process vessel.

Removing Vaporized Compounds

Referring again to FIG. 1 , the method may further include removing anyvaporized compounds released by the heated solid waste mixture at step108. The vaporized compounds may include steam (i.e. water vapor) and/orany one or more of the additional vaporized compounds described herein.The vaporized compounds may be removed by applying a vacuum within theinterior volume of the process vessel after the heating and optionalmixing of the solid waste mixture at step 106. The vacuum may begenerated by a vacuum system attached to the process vessel at a vacuumport as described herein below. Sweep air may be introduced into theprocess vessel to facilitate the movement of the vaporized compounds outof the vessel.

The vacuum system may continuously remove any vaporized compoundsthroughout the duration of heating and optional mixing conducted at step106. The vacuum pressure maintained within the process vessel mayprevent the combustion of any materials within the solid waste mixtureand associated energy loss as it is dried and heated. Without beinglimited to any particular theory, the vacuum pressure within the processvessel may also lower the vaporization temperatures of the water andother vaporized compounds described herein above, thereby decreasing thetime needed to remove any vaporized compounds from the solid wastemixture. As described herein, sweep air may be introduced into theprocess vessel to facilitate the movement of the vaporized compounds outof the vessel.

The vacuum system may comprise a condenser. The condenser may comprisean upper port, a lower port below the upper port, a condensate basinbelow the lower port, and a drain in the condensate basin. When present,the condenser is operatively coupled to the vacuum port of the processvessel via the upper port of the condenser, and the condenser isoperatively coupled to the vacuum pump via the lower port of thecondenser. The vacuum pump and condenser rapidly remove the vaporizedcompounds) during processing to produce a condensate in the condenser,thereby preparing the fuel composition for pyrolysis without pyrolyzingthe material.

The pressure maintained within the process vessel may less than about6.67 kPa (50 torr), 6.00 kPa (45 torr), 5.33 kPa (40 torr), 4.67 kPa (35torr), 4.00 kPa (30 torr), 3.33 kPa (25 torr), 2.67 kPa (20 torr), 2.00kPa (15 torr), 1.33 kPa (10 torr), or 0.67 kPa (5 torr). The pressuremaintained within the process vessel may be less than about 4.67 kPa (35torr). The pressure maintained within the process vessel may be lessthan about 3.33 kPa (25 torr).

The range of pressures maintained within the process vessel can and willvary. The pressure is between about 5 torr about 100 torr, such asbetween about 5 torr and 10 torr, between about 10 torr and 15 torr,between about 15 torr and 20 torr, between about 20 torr and 25 torr,between about 25 torr and 30 torr, between about 30 torr and 35 torr,between about 35 torr and 40 torr, between about 40 torr and 45 torr,between about 45 torr and 50 torr, between about 50 torr and 55 torr,between about 55 torr and 60 torr, between about 60 torr and 65 torr,between about 65 torr and 70 torr, between about 70 torr and 75 torr,between about 75 torr and 80 torr, between about 80 torr and 85 torr,between about 85 torr and 90 torr, between about 90 torr and 95 torr,and between about 95 torr and 100 torr.

The pressure maintained within the process vessel may be between about40 torr and about 60 torr. The vaporized compounds removed from theprocess vessel at step 108 may include steam (water vapor) as well asone or more of the additional vaporized compounds described herein. Thevaporized compounds may be additionally treated to produce recycledwastewater, as illustrated in FIG. 3 .

FIG. 3 is a flowchart illustrating a method 300 of additionally treatingthe mixture of vaporized compounds removed from the process chamber. Themethod 300 includes removing the vaporized compounds released by theheated solid waste mixture at step 302 and condensing the vaporizedcompounds to produce wastewater at step 304. The condensed wastewatermay include one or more of the additional vaporized compounds including,but not limited to, chlorine and various organic solvents, in an aqueoussolution. The vaporized compounds may have a temperature above about100° C. This temperature may fall above the maximum operationaltemperature of various water treatment devices included in the vacuumsystem. By way of non-limiting example, a membrane filter may have amaximum operating temperature of about 85° C. and an activated carbonfilter may have a maximum operating temperature of about 35° C.

Referring again to FIG. 3 , the condensed wastewater may be cooled atstep 306. The condensed wastewater may be stored in a wastewater tankexposed to atmospheric temperature conditions ranging from about −40° C.(−40° F.) to about +40° C. (100° F.) and allowed to cool. The wastewatertank may be constructed of a material with relatively high heatconductivity including, but not limited to, a metal material. Thewastewater storage tank may be constructed from stainless steel. Thewastewater tank may further include a water circulation device such as astirrer or pump to circulate the wastewater within the tank to enhancethe rate of cooling. The condensed wastewater may be cooled at step 306to a temperature of less than about 85° C. prior to subjecting thecondensed wastewater to additional water treatment devices as describedherein below. The wastewater may be cooled at step 306 to a temperatureof less than about 80° C., less than about 75° C., less than about 70°C., less than about 65° C., less than about 60° C., less than about 55°C., less than about 50° C., less than about 45° C., less than about 40°C., less than about 35° C., less than about 30° C., and less than about25° C.

Referring again to FIG. 3 , the method of treating the condensedwastewater may further include filtering the condensed wastewaterthrough a membrane filter at step 308. Without being limited to anyparticular theory, the membrane filter may remove dissolved compoundsincluding, but not limited to, one or more of the organic solventsdescribed herein above. Any known membrane filter may be used at step308 including, but not limited to, an asymmetrical polyether sulphonemembrane filter, a Nylon™ (polyamide) membrane filter, and a Teflon™(polytetrafluoroethylene, PTFE) membrane filter. The wastewater may becooled to a temperature of less than about 85° C. prior to beingsubjected to membrane filtration at step 308. The wastewater may becooled prior to step 308 to a temperature of less than about 80° C.,less than about 75° C., less than about 70° C., less than about 65° C.,less than about 60° C., less than about 55° C., less than about 50° C.,less than about 45° C., less than about 40° C., less than about 35° C.,less than about 30° C., and less than about 25° C.

Referring again to FIG. 3 , the method of treating the condensedwastewater may further include subjecting the wastewater to an ozonetreatment at step 310. Without being limited to any particular theory,the ozone treatment may destroy and bacteria within the wastewater,rendering the wastewater sterile. Because the solubility of ozone inwater is enhanced at cooler water temperatures, the water may beadditionally cooled prior to step 310. The water may be filtered throughthe membrane filter at step 308 prior to the ozone treatment at step310, thereby providing additional time for the wastewater to cool. Thewastewater subjected to the ozone treatment at step 310 may be cooled toa temperature of less than about 40° C. The wastewater may be cooledprior to step 308 to a temperature of less than about 35° C., less thanabout 30° C., less than about 25° C., and less than about 20° C.

Referring again to FIG. 3 , the wastewater may be filtered using anactivated carbon filter at step 312. Without being limited to anyparticular theory, the activated carbon filter may remove chlorine gas,sediment, volatile organic compounds (VOCs), chlorinated organiccompounds, taste, and odor from the wastewater. In addition, theadsorption process by which the activated carbon removes thecontaminants from the wastewater may be enhanced at relatively low watertemperatures. The water may be filtered through the membrane filter atstep 308 and subjected to the ozone treatment at step 310 prior to theactivated carbon filtration at step 312, thereby providing additionaltime for the wastewater to cool. The wastewater may be cooled to atemperature of less than about 40° C. prior to filtration through theactivated carbon filter at step 312. The wastewater may be cooled priorto step 312 to a temperature of less than about 35° C., less than about30° C., less than about 25° C., and less than about 20° C.

The wastewater treated at steps 308, 310, and 312 may be discharged assewage or may be stored for subsequent use at step 314. Non-limitingexamples of suitable subsequent uses for the treated wastewater includedust control and irrigation of nonfood crops such as energy crops.

Heat and Mix Dried Solid Waste Mixture

The dried solid waste mixture remaining in the process vessel afterremoving the vaporized compounds at step 108 may be further heated andmixed to a final temperature to at least about 160° C. at step 109. Thefinal temperature must be sufficiently high to melt plastic materialwithin the dried solid waste mixture. Without being limited to anyparticular theory, the admixing of the melted plastic with the othermaterials of the solid waste mixture may bind together and reduce theporosity of the resulting solid fuel composition. The melted plasticsincrease the density, increase the energy content, enhance of the wasteresistance, and improve the downstream processing of the resulting solidfuel composition.

The final temperature of the dried solid mixture may depend on any oneor more of at least several factors including, but not limited to, thecomposition of the solid waste mixture. If the solid waste mixtureincludes any chlorine-containing plastics, the final temperature may beelevated to a temperature sufficient to liberate the chlorine from thesolid waste mixture, as described herein. The highest meltingtemperature of a plastic mixture included in the solid waste mixture maydetermine the final temperature, to ensure that all plastics in thesolid waste mixture are melted.

FIG. 2 is a graph schematically illustrating the temperature profile ofa solid waste mixture within the process vessel after introduction intothe vessel at an initial time t=0. At a first temperature range 202, thesolid waste mixture is heated from an initial temperature correspondingto the ambient temperature to a temperature of about 100° C. As thetemperature of the solid waste increases up to and beyond about 100° C.,the moisture and other volatile compounds within the solid waste mixturemay be vaporized and released as a mixture of vaporized compounds,thereby separating the solid waste mixture into the vaporized compoundsand a dried solid waste mixture. For example and by way of observation,at temperature above about 190° C. chlorinated organic compounds andchlorine gas are liberated from the solid waste mixture.

Mixing the solid waste mixture enhances the release of the steam byreplenishing the outer surface from which the steam may be released, aswell as compressing the solid waste mixture to squeeze out any voids orvapor bubbles formed within the solid waste mixture. In addition to therelease of steam and other vaporized compounds, the solid waste mixturemay also be sterilized within the second temperature range 204.

Referring again to FIG. 2 , as the temperature increases beyond about200° C., various organic compounds within the solid waste mixture may bebroken down. Within the third temperature range from about 200° C. toabout 240° C., various volatile compounds may be liberated from anyplastics included within the solid waste mixture and released asadditional vaporized compounds in addition to any steam that maycontinue to be released. Chlorine may be released fromchlorine-containing plastics including, but not limited to, polyvinylchloride (PVC) plastics. Various organic solvents may be released fromthe heated solid waste mixture.

Non-limiting examples of other additional vaporized compounds that maybe released during the heating of the solid waste mixture includeacetone, benzene, carbon disulfide, chloromethane, ethyl acetate,2-hexanone, methyl ethyl ketone, styrene, butyl alcohol, THF, toluene,benzyl alcohol, bis(2-chloroethoxy)methane, diethyl phthalate,dimethylphthalate, di phenhydrazine, bis(2-ethylhexyl)phthalate,isophorone, methyphenol, nitrobenzene, nitrophenol, nitrosodi-n-propylamine, o-toluidine, hexanedioic acid, bis(2-ethylhexyl)ester,tetracosahexaene, and furanmethanol.

As the temperature increases above about 240° C. into the fourthtemperature range 208, plastic material within the solid waste mixturemust be melted and admixed with the other constituents of the solidwaste mixture. The maximum temperature of the solid waste mixture mayrange between about 160° C. and about 300° C. The maximum temperaturemay be about 160° C., about 170° C., about 180° C., about 190° C., about200° C., about 210° C., about 220° C., about 230° C., about 240° C.,about 245° C., about 250° C., about 255° C., about 260° C., about 265°C., about 270° C., about 275° C., about 280° C., about 285° C., about290° C., about 295° C., and about 300° C. The maximum temperature may beabout 190° C. The maximum temperature may be about 260° C., asillustrated in FIG. 2 . The maximum temperature and processingconditions should be controlled such that the solid waste mixture doesnot pyrolyze.

The one or more heated walls may be maintained at a temperaturecorresponding to the maximum temperature of the solid waste mixture. Theone or more heated walls may be maintained at a temperature higher thanthe maximum temperature of the solid waste mixture. By maintaining theone or more heated walls at a higher temperature, the solid wastemixture may be heated up to the maximum temperature in a shorter time.

The one or more heated walls may be maintained at a temperature that maybe about 30° C. higher than the maximum temperature of the solid wastemixture. The one or more heated walls may be maintained at a temperaturethat may be about 30° C. higher, about 40° C. higher, about 50° C.higher, about 60° C. higher, about 70° C. higher, about 80° C. higher,about 90° C. higher, about 100° C. higher, about 120° C. higher, about140° C. higher, about 160° C. higher, about 180° C. higher, and about200° C. higher than the maximum temperature of the solid waste mixtureprior to extrusion. The maximum temperature and processing conditionsshould be controlled such that the solid waste mixture does notpyrolyze.

The solid waste mixture may be heated within the process vessel for aduration ranging from about 15 minutes to about 120 minutes to permitsufficient time for the solid waste mixture to homogenize and for themixed plastics to melt. The duration of heating may depend on any one ormore of at least several factors including, but not limited to, thesolid waste mixture introduced into the process vessel, the temperatureof the one or more heated walls, the specific heats of the variousconstituents of the solid waste mixture, and the mixing speed. The solidwaste mixture may be heated for a duration ranging from about 15 minutesto about 25 minutes, from about 20 minutes to about 30 minutes, fromabout 25 minutes to about 35 minutes, from about 30 minutes to about 40minutes, from about 35 minutes to about 45 minutes, from about 40minutes to about 50 minutes, from about 45 minutes to about 55 minutes,from about 50 minutes to about 60 minutes, from about 55 minutes toabout 65 minutes, from about 60 minutes to about 90 minutes, from about75 minutes to about 105 minutes, and from about 90 minutes to about 120minutes. The solid waste mixture may be heated within the process vesselfor a duration of about 30 minutes. The solid waste mixture may beheated within the process vessel for a duration of about 60 minutes.

The duration of mixing and heating performed on the solid waste mixtureat step 109 may be determined by any one or more of at least severalmethods. The process vessel may include a sighting glass through whichan operator of the system may visually monitor the solid waste mixtureas it is heated and mixed within the process vessel. The operator of thesystem may manually deactivate the mixer when the operator observes thatthe solid waste mixture has been converted to the solid fuelcomposition. By way of non-limiting example, the operator may manuallydeactivate the mixer when the plastics within the solid waste mixtureare observed to be melted and admixed with the other constituents of thesolid waste mixture.

The method may include monitoring the temperature of the solid wastemixture as it is heated and mixed at step 109. The temperature may bemonitored using a temperature sensor included in the process vessel asdescribed herein. The monitored temperature of the solid waste mixturemay be displayed to an operator of the system and used to determine theduration of heating and mixing in step 109. By way of non-limitingexample, the operator of the system may deactivate the mixer when thedisplayed temperature of the solid waste mixture within the processvessel exceeds a maximum temperature described herein above. Themeasured temperature of the solid waste mixture may be communicated toan automated control system. The automated control system may deactivatethe mixer when the measured temperature of the solid waste mixtureexceeds the maximum temperature described herein previously.

The process vessel may include a single interior volume within which theheating and mixing of steps 106 and 109 are conducted. The processvessel may include an interior wall dividing the interior volume into adrying chamber and a mixing chamber. The heating of the solid wastemixture at step 106 may occur within the drying chamber, followed by theremoval of the vaporized compounds at step 108 within the same dryingchamber. Also, the dried solid mixture remaining in the drying chamberafter step 108 may transferred into the mixing chamber through atransfer opening contained within the interior wall. Optionally, themixing chamber may also include a vacuum attachment fitting to enablethe application of vacuum from the vacuum assembly to eitherperiodically apply a vacuum to the mixing chamber or to maintain avacuum within the mixing chamber to remove any additional vaporizedcompounds released during the heating of the dried solid waste mixture.

Extrusion of Heated Solid Waste Mixture

Referring again to FIG. 1 , after heating and mixing the dried solidwaste mixture at step 109 and optionally removing any residual steam andother vaporized compounds released during heating to the finaltemperature, the dried solid waste mixture may have formed into a heatedsolid waste mixture made up of a relatively uniform viscous material inwhich the melted plastics are distributed throughout the material. Theheated solid waste mixture may be extruded from the process vessel atstep 110.

The heated solid waste may be extruded from the process vessel using anyextrusion method known in the art without limitation. The process vesselmay be provided with an extruder outlet as described herein below. Theextruder outlet may include a cross-sectional profile with a variety ofshapes and dimensions. The cross-sectional profile of the extruderoutlet may be selected to produce a solid fuel composition with a shapethat facilitates handling, transportation, storage, and/or subsequentuse. Non-limiting examples of suitable cross-sectional profile shapesinclude circular, triangular, square, or any other closed polygonalshape.

The maximum dimension of the cross-sectional profile of the extruderoutlet may vary from about 1 inch to about 12 inches or larger. Themaximum dimension may vary from about 1 inch to about 3 inches, fromabout 2 inches to about 4 inches, from about 3 inches to about 5 inches,from about 4 inches to about 6 inches, from about 5 inches to about 7inches, from about 6 inches to about 8 inches, from about 7 inches toabout 9 inches, from about 8 inches to about 10 inches, from about 9inches to about 11 inches, and from about 10 inches to about 12 inches.The cross-sectional profile of the extruder outlet may be a square shapewith a maximum dimension of 2 inches.

The process vessel may be provided with any known device to compress theheated solid waste mixture through the extruder outlet withoutlimitation. The process vessel may be provided with a mixer thatincludes a screw conveyor that may be operated in one direction duringthe mixing phase and may be operated in a reverse direction to extrudethe heated solid waste mixture. The process vessel may include a screwconveyer within a partially enclosed channel within a bottom portion ofthe vessel wall. The screw conveyer may be activated to initiate theextrusion of the heated solid waste mixture at step 110.

The heated solid waste mixture may cool as it extruded into the coolertemperatures outside of the process vessel. The extruder outlet may beheated to maintain the temperature of the heated solid waste mixture atan extrusion temperature. Without being limited to any particulartheory, the extrusion temperature may be selected to maintain aviscosity within the heated solid waste mixture compatible withextrusion using the extrusion elements provided in the process vessel.The extruder outlet may be heated using any known heating methodincluding, but not limited to, an electrical resistive heater, a heatedjacket, an inductive heater, and any other known suitable heatingmethods.

The heated solid waste mixture may emerge from the extruder outlet at atemperature below the maximum temperature of the heated solid wastemixture within the process vessel. The temperature of the extruded solidwaste mixture may range from about 100° C. to about 260° C. Thetemperature of the extruded solid waste mixture may range from about100° C. to about 140° C., from about 120° C. to about 160° C., fromabout 140° C. to about 180° C., from about 160° C. to about 200° C.,from about 180° C. to about 220° C., from about 200° C. to about 240°C., and from about 220° C. to about 260° C.

The temperature of the extruded solid waste mixture may be about 200° C.The extruded solid waste mixture may be below about 200° C. Althoughhigher temperatures have been used, pyrolysis of the extruded solidwaste mixture has been observed to occur at extrusion temperatures above200° C.

The extruded solid waste mixture may optionally be cut into pieces as itis extruded. Any known devices for cutting extruded materials may beused to cut the extruded solid waste mixture including, but not limitedto, laser cutters, saws, water jet cutters, and any other suitablecutting device. The extruded waste mixture may be cooled slightly toharden the material prior to cutting. The extruded solid waste mixturemay be cut into pieces less than about two feet in length.

The extruded solid waste mixture may be cooled at ambient temperatureconditions outside of the process vessel. The cooling rate of theextruded solid waste mixture may be accelerated using one or morecooling devices or methods. The extruded solid waste mixture may becooled using one or more devices to enhance heat transfer away from theextruded waste mixture including, but not limited to, air fans, mistingfans, water cooling tanks, chilled surfaces, refrigerated chambers, andany other known material cooling device. A conveyor, such as awater-cooled conveyor, may be used to allow the extruded solid waste tocool to form a solid fuel composition.

The extruded solid waste mixture may be rapidly cooled; that is, cooledfaster than leaving the mixture under ambient conditions. Doing so maypromote solidification and storage stability. The time taken to cool theextruded solid waste can and will vary. The time for the extruded solidwaste mixture to cool may about 15 minutes, about 14 minutes, about 13minutes, about 12 minutes, about 11 minutes, about 10 minutes, about 9minutes, about 8 minutes, about 7 minutes, about 6 minutes, about 5minutes, about 4 minutes, about 3 minutes, about 2 minutes, about 1minutes, about 30 seconds, or about 15 seconds. The extruded solid wastemixture may cool in less than 10 minutes. The extruded solid wastemixture may cool in less than 5 minutes. The extruded solid wastemixture may cool in less than 1 minute.

The solid waste mixture may be formed into pieces using a method otherthan extrusion. Any known method of forming a viscous material into adesired shape may be used to form the pieces including, but not limitedto, compression molding. By way of non-limiting example, the heatedsolid waste mixture may be removed from the process vessel and dividedinto a plurality of molds and compressed into a desired shape. Thedesired shape may be similar to the shape of the pieces formed using anextrusion method as described herein above. The desired shape may be arod with a maximum cross-section of about two inches and a rod length ofabout 2 feet. The cross-sectional profile of the desired shape may be acircle, a square, or any other suitable cross-sectional profile.

The extruded solid waste mixture may be cooled to form the solid fuelcomposition. The resulting solid fuel composition is sterile,hydrophobic, chemically stable, and/or non-biodegradable. “Sterile”refers to the solid fuel composition being substantially free of livingmicroorganisms, such as bacteria, fungi, and viruses, after beingproduced. “Stable” or “chemically stable” refers to solid fuelcomposition not substantially changing its chemical or physicalproperties or structure upon extended contact with water, oxygen, orambient conditions, especially under ordinary storage conditions. Thesolid fuel composition is “stable” until it is combusted, pyrolyzed, oremployed as feedstock in a similar process. “Non-biodegradable” refersto the solid fuel composition not degrading or deposing under ordinarybiological action, such as rot or composting. As a result, the solidfuel composition may be stored for extended periods at a wide range ofstorage conditions, used as feedstock to a collocated waste-to-energyfacility, transported to a remote waste-to-energy facility, and/or usedto provide energy for the process vessel and associated devices.

The solid fuel composition pieces may be optionally ground into smallerpieces suitable for use as a feedstock to a pyrolysis reactor. Theparticle size of the smaller pieces may vary depending on the particularpyrolysis reactor for which the solid fuel composition may be used as afeedstock. The particle size of the smaller pieces may range in particlesize from about 0.1 mm to about 10 mm. The smaller pieces may have amaximum particle size of about 3 mm. The ground pieces of the solid fuelcomposition may be formed into a building material by extruding thesolid fuel composition into a lumber profile using known equipment andmethods.

II. System for Forming Solid Fuel Composition

A system for producing a solid fuel composition from a solid wastemixture is provided. FIG. 7 is a generalized schematic of a system forprocessing mixed solid wastes, as disclosed herein. System 700 comprisesa process vessel 710, a heater 720, a condenser 730, a vacuum pump 740,a control panel 750, a conveyor 760, and one or more optional watertreatment devices 770. The process vessel 710 comprises a mixer 712within the interior volume of the process vessel 710 and operativelyconnected to the process vessel 710. The process vessel 710 also has anextruding element 716 passing through a first opening in the processvessel 710, and a vacuum port 714 passing through a second opening inthe process vessel 710. The heater 720 is operatively connected to theprocess vessel 710 to heat the interior volume of the process vessel710, for example by heating one or more walls of the process vessel 710.

The condenser 730 comprises an upper port 734 and a lower port 736. Thecondenser is operatively coupled to the vacuum port 714 of the processvessel 710 via the upper port 734 of the condenser 730. The vacuum pump740 is operatively coupled to the condenser 730 via the lower port 736of the condenser 730. The control panel 750 is operatively connected tothe mixer 712, the heater 720, the vacuum pump 740, and one or moreoptional sensors within the system 700. The conveyor 760, acting as acooling unit, is operatively connected to the extruding port 716 of theprocess vessel 710 to receive extruded material. More detail can befound in the subparts described herein. Optional filters 770 may beoperatively connected to condenser 730 to treat condensate formed in thecondenser 730 during operation of the system 700.

FIG. 4 is a block diagram illustrating the elements of the system 400.The system 400 may include a process vessel 401 operatively connected toa heater 405 and a vacuum system 403. The process vessel may include amixer 408 to mix the solid waste mixture as it is heated by the heater405. In addition, the vacuum system 403 maintains a relatively oxygenfree atmosphere within the process vessel 401 and additionally removeswater vapor and other vaporized compounds as they are released from theheated solid waste mixture within the process vessel 401. The systemprovides the devices and elements suitable for carrying out the processof forming a solid fuel composition as described herein.

Process Vessel

Referring to FIG. 4 , the system 400 may include a process vessel 401.The process vessel 401 comprises one or more heated walls maintained ata wall temperature, a mixer 408 in the interior volume of the processvessel and operatively connected to the process vessel 401, an extrudingelement passing through a first opening in the process vessel 401, and avacuum port passing through a second opening in the process vessel. Theprocess vessel 401 encloses an internal volume 406 containing a mixer408. The solid waste mixture may be introduced into the internal volume406 and agitated using the mixer 408 and heated using the heater 405operatively coupled to the vessel 401. The pressure within the internalvolume 406 may be maintained at a vacuum pressure below about 50 torrusing the vacuum system operatively coupled to the vessel 401 via thevacuum port. The process vessel 401 may be constructed of any knownmaterial with suitable strength, non-reactivity, and/or heat resistanceup to at least a maximum temperature of about 300° C. The material ofthe vessel 401 may have a high heat conductivity to facilitate theheating of the internal volume by the heater 405. The material of theprocess vessel 401 may be compatible with particular heating methods,including, but not limited to, conduction heating and inductive heating.The process vessel 401 may be constructed of a metal including, but notlimited to, stainless steel.

The process vessel 401 may vary in overall size depending on any one ormore of at least several factors, including, but not limited to, thesolid waste mixture to be mixed within the vessel 401, the type of mixer408 included within the vessel 401, and/or the desired footprint of thevessel 401 at the waste-to-energy facility or other site at which thesystem 400 is to be operated.

The process vessel 401 may be provided as an essentially rectangularcontainer. The length of the process vessel 401 may range from about 5feet to about 20 feet. The height and width of the process vessel 401may each range from about 5 feet to about 10 feet. The process vessel401 may have a length of about 10 feet, a width of about 7 feet and aheight of about 7 feet.

Referring again to FIG. 4 , the process vessel 401 may further includeone or more openings, ports, and/or hatches to provide access to/fromthe internal volume 406 of the vessel 401 and/or to provide operativecoupling of one or more devices associated with the system including,but not limited to, the vacuum system. Non-limiting examples of the oneor more openings include an exhaust port 420, an extrusion outlet 434,and an inlet 444. The one or more openings of the vessel are describedin further detail herein below.

Resealing Opening/Optional Hopper

The solid waste mixture may be introduced into the internal volume 406of the process vessel 401 to initiate the method of forming the solidfuel composition as described herein above. The solid waste mixture maybe introduced into the internal volume 406 via a resealing openingincluding a hatch, a door, a port, or any other suitable resealingopening formed in a vessel wall. The resealing opening may be opened toinsert the solid waste mixture into the vessel 401, and subsequentlyprior to initiating the heating and mixing within the process vessel401. The resealing opening may be provided with seals, gaskets, and/orany other features to form an airtight seal when the resealing openingis closed.

Referring again to FIG. 4 , the system 400 may optionally include ahopper 402 operatively coupled to the process vessel 401 to collect andintroduce the solid waste mixture 404 into the internal volume 406 ofthe vessel 401. The hopper 402 may be coupled to the internal volume 406via a solid waste inlet 444 provided within a vessel wall. The solidwaste inlet 444 may be a resealing door configured to open and empty thesolid waste mixture 404 from the hopper 402 into the internal volume406. The resealing door may close and form a seal once the solid wastemixture is transferred from the hopper 402 into the internal volume 406.These configurations are suitable for batch processing, continuousprocessing, or semicontinuous processing.

Any known hopper design known in the art may be selected as the hopper402 included in the system 400. The hopper 402 may further include ashredder (not shown) to shred the solid waste mixture into piecessuitable for mixing and heating within the process vessel 401 asdescribed herein. In particular, the solid waste may be heated and mixedwithin the process vessel 401 under reduced pressure. A shredder may beoperatively coupled to the vessel 401 via the solid waste inlet 444. Theexit port of the shredder may feed the solid waste mixture into theinternal volume 406. Any known shredder design may be suitable forinclusion in the system 400 including, but not limited to, a singleshaft rotary shredder, a dual-shaft rotary shredder, a granulator, and ahammer mill shredder.

Mixer

Referring again to FIG. 4 , the process vessel 401 may further include amixer 408 to mix the solid waste mixture within the internal volume 406.Any known mixer design may be included in the process vessel withoutlimitation. The mixer 408 may be selected based on any one or more of atleast several factors including, but not limited to, ability to agitatethe relatively dense and viscous solid waste mixture; ability to impartshear forces to the solid waste mixture; and energy requirements todrive the mixer. The mixer 408 may include at least one mixer blade 446.

The one or more mixer blades 446 may be oriented within the internalvolume 406 such the axis of rotation of the one or more mixer blades 446is aligned along the length of the vessel 401. Any suitable mixer bladedesign may be selected for inclusion in the system including, but notlimited to, a screw conveyer and a naben blade.

The process vessel 401A may include dual mixer blades 502/504. The dualmixer blades 502/504 may counter-rotate to enhance the mixing of thesolid waste mixture within the internal volume 406. By way ofnon-limiting example, the first mixer blade 502 may rotate in aclockwise direction and the second mixer blade 504 may rotate in acounterclockwise direction. In the example, the counter-rotating mixerblades 502/504 may carry solid waste mixture from the lower portion ofthe internal volume 406 to the upper portion, and would additionallyforce solid waste mixture from the upper portion of the internal volumedownward between the mixer blades 502/504. The dual mixer blades 502/504may be laterally spaced in close proximity to enable the grinding of thesolid waste mixture between the mixer blades 502/504. The lateralspacing of the mixer blades 502/504 may provide a slight gap throughwhich hard particles such as metal or ceramic bits may pass withoutjamming between the mixer blades 502/504.

Dual Chamber Process Vessel

The interior volume 406 of the process vessel 401 may be subdivided intoseparate drying and mixing chambers. FIG. 6 is a cross-sectional view ofa process vessel 401B that includes an interior wall 702 that subdividesthe interior volume into a drying chamber 704 and a mixing chamber 706.Both chambers 704/706 may be surrounded by a heated jacket to heat thecontents of both the drying chamber 704 and the mixing chamber 706. Theinterior wall 702 may further contain a resealing door 708 that may opento transfer the contents of the drying chamber 704 into the mixingchamber 706.

The dual-chamber process vessel 401B may further include a mixer 408situated within the mixing chamber 706. A second mixer 408A (not shown)may be situated within the drying chamber 704. The dual-chamber processvessel 401B may further include an extruder outlet 434 to provide aconduit through which the heated solid waste mixture may be extrudedfrom the mixing chamber 706 and out of the vessel 401B.

Vacuum System

Referring again to FIG. 4 , the process vessel 401 may be operativelycoupled to the vacuum system 403. The process vessel 401 may include anexhaust port 420 to provide an operative coupling to the vacuum system403. The exhaust port 420 may form a channel 438 opening to the internalvolume 406 at an internal end 440 and to the exterior of the vessel 401at the external end 442. The vacuum system 403 may be attached to theexternal end 442 of the exhaust port 420. The vacuum system 403 may beconnected to the exhaust vent 420 via a vacuum hose 422.

The vacuum hose 422 may be reinforced to prevent collapse during use.The vacuum hose 422 may also be heat-resistant to ensure safe operationat temperatures up to the maximum temperature to which the solid wastemixture may be heated. The vacuum hose may be heat-resistant up to atemperature of about 300° C. The vacuum hose 422 may be chemically inertand/or corrosion resistant to resist degradation from any vaporizedcompounds removed from the internal volume 406 during heating of thesolid waste mixture. The vacuum hose 422 may be a heavy steel-lined highheat hose.

Referring again to FIG. 4 , the vacuum system 403 may include a vacuumpump 424. The vacuum pump 424 may be selected to maintain a sufficientlylow pressure as described herein within the internal volume 406. Inaddition, the vacuum pump 424 may be chemically inert, heat resistant,and/or corrosion resistant. Further, the vacuum pump 424 may besufficiently rugged to operate in the presence of any particles or othersolid contaminants transferred from the internal volume 406. The vacuumpump 424 may be placed on a stand or a raised platform to prevent itfrom exposure to water during incidental flooding.

Any vacuum pump design may be included in the vacuum system 403 withoutlimitation. Non-limiting examples of suitable vacuum pumps include arotary vane pump, a diaphragm pump, and a liquid ring pump. The vacuumpump 424 may be a liquid ring pump. The vacuum pump 424 may be two ormore liquid ring pumps connected in series. As described herein above,the vacuum pump 424 may maintain a pressure of less than about 50 torrwithin the internal volume 406 and may further remove any water vaporand/or other vaporized compounds released by the heated solid wastemixture into the internal volume 406.

Referring again to FIG. 4 , an air source 454 may be operatively coupledto the process vessel 401 via an air inlet 452. The air source mayintroduce sweep air into the interior volume 406 of the process vessel401 to facilitate the movement of the vaporized compounds out of theinterior volume 406 and into the vacuum system 403. The air inlet mayprovide air at a flow rate selected to maintain a vacuum pressure ofless than about 50 torr within the interior volume 406 when the vacuumsystem 403 is activated. The air source may be any known air sourceincluding, but not limited to, a compressed air tank; an air compressor,air pump, or fan drawing in atmospheric air, and any other known airsource. The air source may supply an oxygen-free and non-reactive gasincluding, but not limited to, nitrogen and any noble gas such as argon.

The sweep air supplied by the air source 454 may be heated prior tointroduction into the interior volume 406. The temperature of the sweepair may range from about 20° C. to about 280° C. The temperature of thesweep air may be at least 20° C., at least 40° C., at least 60° C., atleast 80° C., at least 100° C., at least 120° C., at least 140° C., andat least 160° C. The sweep air may be heated using a dedicated sweep airheater operatively coupled to the air source 454. The sweep air may bedirected through a heat-exchanging device to transfer waste heat fromthe heater 405 to the sweep air. The high temperature exhaust of theheater 405 may be directed into the air source 454 for use as sweep air.

Referring again to FIG. 4 , the vacuum system 403 may further include acondenser 426 operatively connected to the vacuum pump 424 and to theprocess vessel 401 via the vacuum hose 422. The condenser 426 cools thewater vapor and/or other vaporized compounds drawn from the processvessel 401 by the vacuum pump 424 to produce wastewater. The wastewatermay be transferred to a cooling tank 428 that is also operativelyconnected to the condenser 428.

The cooling tank 428 may be any tank capable of holding a heated liquidthat may include one or more of the vaporized compounds as describedherein above. The cooling tank 428 may be constructed of a corrosionresistant and non-reactive material with a relatively high heatconductance to enhance the cooling of the wastewater. A chiller or otheractive cooling device (not shown) may be operatively coupled to thecooling tank 428 to enhance the cooling rate of the wastewater withinthe cooling tank 428.

The vacuum system may comprise a condenser. The condenser may comprisean upper port, a lower port below the upper port, a condensate basinbelow the lower port, and a drain in the condensate basin. When present,the condenser is operatively coupled to the vacuum port of the processvessel via the upper port of the condenser, and the condenser isoperatively coupled to the vacuum pump via the lower port of thecondenser.

As described herein above, the wastewater produced by the condenser 426may include one or more of the additional vaporized compounds including,but not limited to, chlorine and various organic solvents, in an aqueoussolution. Referring again to FIG. 4 , the vacuum system 403 may furtherinclude one or more water treatment devices 430 operatively coupled inseries to the wastewater-cooling tank 428 opposite to the condenser 426.The one or more water treatment devices 430 may be configured to removethe additional vaporized compounds from the condensed water to producetreated wastewater. Non-limiting examples of suitable water treatmentdevices 430 include membrane filters, ozone chambers, and activatedcarbon filters.

The one or more water treatment devices 430 may include a membranefilter. Any suitable membrane filter may be included as a watertreatment device 430 within the vacuum system 403. Non-limiting examplesof suitable membrane filters include an asymmetrical polyether sulphonemembrane filter; a Nylon™ (polyamide) membrane filter; and a Teflon™(polytetrafluoroethylene, PTFE) membrane filter. The membrane filter maybe selected depending on the expected vaporized compounds to be removedfrom the wastewater. In addition, the membrane filter may be selecteddepending on the expected temperature of the wastewater leaving thecooling tank 428. For example, the Teflon™ (polytetrafluoroethylene,PTFE) membrane filter, with a maximum operating temperature of about180° C. may tolerate much higher wastewater temperatures than a Nylon™(polyamide) membrane filter, with a maximum operating temperature ofabout 80° C.

The one or more water treatment devices 430 may include an ozonechamber. The ozone chamber may sterilize the wastewater. An ozonechamber of any known design may be selected as a water treatment device430. As described herein above, the maximum operating temperature of theozone chamber may be about 40° C. Without being limited to anyparticular theory, the effectiveness of the ozone chamber may beenhanced at lower water temperature due to the increased solubility ofozone at lower water temperatures.

The one or more water treatment devices 430 may include an activatedcarbon filter. The activated carbon filter may adsorb any one or more ofthe additional vaporized compounds from the wastewater. As describedherein above, the effectiveness of the adsorption of the vaporizedcompounds to the activated carbon is enhanced at lower watertemperatures. The maximum operating temperature of the activated carbonfilter is about 35° C.

The one or more water treatment devices 430 may be operatively coupledin a linear series so that each device may contact all wastewater to betreated. The sequence of water treatment devices 430 may be arranged tosituate the most robust water treatment devices near the beginning ofthe linear series and to situate the more sensitive water treatmentdevices toward the end of the linear series. A robust water treatmentdevice may be characterized by one or more of the following: relativelyhigh operating temperature; relative insensitivity to a wide range ofsalinity and/or pH; and/or tolerance of fouling with particulate matter.The linear series of the one or more water treatment devices 430 may bearranged according to maximum operational temperature. A membrane filterwith a relatively high maximum operational temperature may be first inthe linear sequence, followed by an ozone chamber, followed by anactivated carbon filter. The cooling tank 428 may cool the wastewater toa temperature below than of the lowest maximum operating temperatureamong the one or more water treatment devices 430, and the one or morewater treatment devices 430 may be arranged in any desired order.

Referring again to FIG. 4 , the vacuum system 403 may further include atreated wastewater holding tank 432 configured to store the wastewatertreated by the one or more water treatment devices 430 for subsequentuse and/or disposal. Any suitable water tank design may be selected forthe wastewater-holding tank 432 without limitation. Thewastewater-holding tank 432 may be constructed out of a wider variety ofmaterials compared to the cooling tank 428 because the treatedwastewater has been cooled and purified as described herein previously.The wastewater-holding tank 432 may be a reinforced fiberglass watertank. As described herein above, the wastewater may be used for dustcontrol, irrigation of non-food crops, and/or disposed of as wastewaterin a sewer system.

Referring again to FIG. 4 , the air remaining in the condenser 426 afterthe vaporized compounds have been condensed may pass through the vacuumpump 424 and may be exhausted into one or more gas scrubbing devices456. The gases exiting the vacuum pump may include air, as well as oneor more additional gases including, but not limited to, methane,chlorine gas, chlorinated organic compounds, and volatile organiccompounds. The one or more gas scrubbing devices 456 may include anadsorbent bed to separate methane and other combustible gases from thevacuum pump exhaust. The methane and other combustible gases captured bythe adsorbent bed may be used to fuel the heater 405, stored for lateruse, and or sold. The one or more gas scrubbing devices 456 may includea gas filter including, but not limited to, an activated carbon filter,a membrane filter, and any other known gas filtration device. The gasremaining after treatment by all of the one or more gas scrubbingdevices 456 may be exhausted to the atmosphere via an exhaust port 458.

Heater

Referring again to FIG. 4 , the system 400 may include a heater 405operatively coupled to the process vessel 401. Any suitable heaterdesign may be selected as the heater 405 including, but not limited to,an electrical heater, an inductive heater, and a convective heater suchas a heated oil jacket. The heater 405 may transfer heat into theinternal volume 408 via one or more heated walls 448 forming theboundary of the internal volume 408. The solid waste mixture may beheated within the internal volume 406 via conduction from the heater 405to the heated wall 448 and via conduction from the heated wall 448 to aportion of the solid waste mixture contacting the heated wall 448.

The heater 405 may be a heated jacket surrounding the process vessel401. The heated jacket may include a hollow shell 410 containing heatedoil 412 circulating within the hollow shell between a heated oil inlet414 and a heated oil exit 416. The temperature of the heated oil 412 maybe increased by passing the oil 412 through a heat exchanger 418configured to transfer heat into the oil 412 as it passes between theheated oil exit 416 and the heated oil inlet 414. The heat exchanger maybe heated by any known heating device including, but not limited to, anelectrical heater, a gas heater, an inductive heater, and any othersuitable heating device. The operation of the heat exchanger 418 may bemodulated using measurements of the heated oil obtained by at least onetemperature sensor situated at one or more locations within the heaterincluding, but not limited to the heated oil inlet 414 and the heatedoil exit 416.

The temperature of the heated oil exiting the heat exchanger 418 may becooled at it circulates back into the heated oil inlet 414. Further, theoil may further cool at it circulates within the hollow shell betweenthe heated oil inlet 414 and the heated oil exit 416. The heat exchanger418 may heat the oil to a temperature of up to about 500° C. or higherat the exit of the heat exchanger 418, depending on the extent ofcooling during transport to the heated oil inlet 414. The oil exitingthe heat exchanger 418 may be heated to at least 300° C., at least 420°C., at least 440° C., at least 460° C., and at least 480° C.

The heated oil may be introduced into the oil inlet at a temperatureranging from about 160° C. to about 330° C. The heated oil may beintroduced into the oil inlet at a temperature of above about 300° C.,such as above 350° C.

The heating oil may degrade over extended use due to acceleratedoxidation at the relatively high temperatures to which the oil isheated. Any known means of maintaining the functional integrity of theheating oil may be used without limitation. A portion of the oil may becontinuously discarded and replaced within the heated oil circuit usingany methods and devices known in the art. The heater may be periodicallydeactivated and the oil may be changed during this inactive period.

The heater 405 may be operated to maintain a relatively constant heatedwall temperature corresponding to a desired maximum temperature of thesolid waste mixture within the process vessel 401, as described herein.The heated wall temperature may be maintained at a wall temperature ofup to about 260° C. The heated wall temperature may be maintained at awall temperature ranging from about 160° C. to about 300° C. The heatedwall temperature may be maintained at a wall temperature of at least160° C., at least 170° C., at least 180° C., at least 190° C., at least200° C., at least 210° C., at least 220° C., at least 230° C., at least240° C., at least 250° C., at least 260° C., at least 270° C., at least280° C., and at least 290° C.

The heated wall temperature may influence the rate at which the solidwaste mixture may be heated up to the final temperature as describedherein above. The heated wall temperature may be maintained at thedesired maximum temperature of the solid waste mixture. The heated walltemperature may be maintained at least 10° C. above the desired maximumtemperature, at least 20° C. above the desired maximum temperature, atleast 30° C. above the desired maximum temperature, at least 40° C.above the desired maximum temperature, at least 50° C. above the desiredmaximum temperature, at least 60° C. above the desired maximumtemperature, at least 70° C. above the desired maximum temperature, atleast 80° C. above the desired maximum temperature, at least 90° C.above the desired maximum temperature, and at least 100° C. above thedesired maximum temperature of the solid waste mixture.

Extruder

The system 400 may further include an extruder to extrude the heatedsolid waste mixture out of the process vessel 401 via the extruderoutlet 434. Referring to FIG. 4 , the process vessel 401 may furtherinclude the extruder outlet 434 to provide a conduit through which theheated solid waste mixture may be extruded from the internal volume 406out of the vessel 401. The extruder may include a compression element tocompress the heated solid waste mixture toward the extruder outlet,thereby forcing the solid waste mixture through the extruder outlet 434.

The compression element may be any suitable compression element known inthe art including, but not limited to a mixer blade, a screw conveyer, apiston, a compression pump, and any other suitable compression element.The compression element may be the mixer blade 446 as illustrated inFIG. 4 and FIG. 6 . The mixer 408 may be operated in a forwardrotational direction during the heating and mixing of the solid wastemixture, and then operated in a reverse rotational direction to compressthe heated solid waste mixture toward the extrusion outlet 434 causingthe extruded solid waste mixture 436 to emerge from the extrusion outlet434.

The compression element may include a dedicated compression element 510separate from the mixer blades 502/504. The compression element 510 mayinclude a screw conveyer situated within a channel 506 formed within alower portion 508 of the vessel wall 512. The extruder outlet 434 may besituated at one end of the channel 506. In use, the compression element510 may be activated when the solid waste mixture has been heated to themaximum temperature ranging from about 160° C. to about 250° C. Thecompression element 510 compresses the heated solid waste mixture withinthe channel 506 toward the one end of the channel adjacent to theextruder outlet 434. In addition, the mixer blades 502/504 arecontinuously operated during extrusion, thereby forcing additionalheated solid waste mixture downward between the mixing blades 502/504toward the channel 506.

FIG. 5 is a cross-sectional view of an extruder outlet 434. The extruderoutlet 434 may include an outlet wall 602 enclosing a lumen opening tothe internal volume 406 at one and to the outside of the process vessel401 at the opposite end. The inner surface 606 of the outlet wall 602may act as an extrusion die to form the cross-sectional shape of theextruded solid waste mixture. The inner surface 606 may define anysuitable extrusion cross-sectional profile as described herein aboveincluding, but not limited to, a circular or square profile. By way ofnon-limiting example, the extrusion cross-sectional profile may be asquare shape as illustrated in FIG. 5 .

The extruder outlet 434 may be heated to facilitate the extrusion of thesolid waste mixture. The extruder outlet 434 may be operativelyconnected to an extrusion heater (not shown) including, but not limitedto, an electrical heater, an inductive heater, and a convective heatersuch as a heated oil jacket. The extrusion heater may transfer heat intothe lumen 604 via the outlet wall 602. The extruding solid waste mixturemay be heated within the lumen 604 via conduction from the heater to theoutlet wall 602 and via conduction from the outlet wall 602 to a portionof the solid waste mixture contacting the outlet wall 602. The heatermay be an additional portion of a heated jacket used to heat theremainder of the process vessel 401. Operating temperatures for theextruder are as described herein and generally should not exceed about200° C.

The system 400 may optionally include a cutter (not shown) configured tocut the extruded solid waste mixture into pieces as it is extruded. Anyknown devices for cutting extruded materials may be selected for use asthe cutter including, but not limited to, laser cutters, saws, water jetcutters, and any other suitable cutting device. The extruded wastemixture may be cooled slightly to harden the material prior to cutting.The extruded solid waste mixture may be cut into pieces less than abouttwo feet in length.

The extruded solid waste mixture may be cooled using one or more devicesto enhance air circulation including, but not limited to, air fans,misting fans, and any other known suitable air circulation device. Thecooling rate of the extruded solid waste mixture may be enhanced byplacing the extruded solid waste mixture on a cooled surface or within acooled chamber including, but not limited to an air-conditioned room orrefrigerated chamber. The extruded solid waste mixture may be immersedin a cooling liquid such as water in a cooling tank 450 as illustratedin FIG. 4 . The extruded solid waste mixture may be extruded onto aconveyer, such as a water-cooled conveyer, to cool the extruded solidwaste mixture and form a solid fuel composition.

Control Panel

The system may comprise a control panel operatively connected to themixer, the heater, and the vacuum pump. The control panel, when present,adjusts the interior volume to a first temperature to vaporize compoundsin a solid waste mixture comprising mixed plastics, adjusts the interiorvolume to a first pressure to remove the vaporized compounds from thesolid waste mixture, to adjusts the interior volume to a secondtemperature between about 160° C. and about 260° C. and to a secondpressure of less than about 50 torr while the mixer is in operation inorder to melt the mixed plastics in the solid waste mixture.

The control panel may further comprise a feedback control systemoperatively connected to one or more sensors. When present, the feedbackcontrol system receives at least one measurement from the one or moresensors and modulates the operation of the vacuum pump, the heater, orthe mixer according to at least one control rule executed in the controlpanel. The one or more sensors monitor one or more operating conditionsof the system. Suitable examples of the one or more sensors include, butare not limited to, a pressure sensor to monitor the pressure within theinterior volume of the process vessel; one or more temperature sensors,each temperature sensor to monitor the temperature of the oil introducedinto the oil inlet of the heated jacket, and the temperature of thesolid waste mixture within the interior volume; a humidity sensor tomonitor the humidity of the vaporized compounds released from theinterior volume; a weight sensor to monitor the weight of the solidwaste mixture within the interior volume, and any combination thereof.

III. Solid Fuel Composition

A solid fuel composition produced from a solid waste mixture using themethods and systems as described herein above is provided. The solidfuel composition may be compatible for use as a feedstock to variouspyrolysis chambers as part of a waste-to-energy process. The method offorming the solid fuel composition results in a material with relativelyuniform consistency and reduced variability in energy content relativeto the solid waste stream used to produce the solid fuel composition.

The solid fuel composition may have an energy content of at least 10,000BTU/lb. The solid fuel composition may have an energy content of atleast 10,000 BTU/lb., at least 11,000 BTU/lb., at least 12,000 BTU/lb.,at least 13,000 BTU/lb., at least 14,000 BTU/lb., and at least 15,000BTU/lb.

The solid fuel composition may have an energy content of at least about8,000 BTU/lb. The solid fuel composition may have an energy content ofat least about 9,000 BTU/lb. The solid fuel composition may have anenergy content of less than about 14,000 BTU/lb. The solid fuelcomposition may have an energy content ranging from between about 8,000BTU/lb. to about 14,000 BTU/lb.

The solid fuel composition may have a density ranging from about 30lb./ft³ to about 80 lb./ft³. The density of the solid fuel compositionmay be at least 30 lb./ft³, at least 40 lb./ft³, at least 50 lb./ft³, atleast 60 lb./ft³, and at least 70 lb./ft³. The solid fuel compositionmay have a density of about 50 lb./ft³.

As described herein, the solid fuel composition may also be chemicallystable, non-biodegradable, and/or hydrophobic, thereby enabling thesolid fuel composition to be stored at a wide range of storageconditions without degrading or reducing energy content. Without beinglimited to any particular theory, the plastic content of the solid wastemixture is melted and distributed throughout the resulting solid fuelcomposition, rendering the composition non-biodegradable, and/orhydrophobic.

The solid fuel composition may include from about 40% wt. to about 80%wt. carbon. The solid fuel composition may include from about 40% wt. toabout 44% wt., from about 42% wt. to about 46% wt., from about 44% wt.to about 48% wt., from about 46% wt. to about 50% wt., from about 48%wt. to about 52% wt., from about 50% wt. to about 54% wt., from about52% wt. to about 56% wt., from about 54% wt. to about 58% wt., fromabout 56% wt. to about 62% wt., from about 60% wt. to about 64% wt.,from about 62% wt. to about 66% wt., from about 64% wt. to about 68%wt., from about 66% wt. to about 70% wt., from about 68% wt. to about72% wt., from about 70% wt. to about 74% wt., from about 72% wt. toabout 76% wt., from about 74% wt. to about 78% wt., and from about 76%wt. to about 80% wt. carbon.

The solid fuel composition may include from about 5% wt. to about 20%wt. hydrogen. The solid fuel composition may include from about 5% wt.to about 7% wt. hydrogen, from about 6% wt. to about 8% wt. hydrogen,from about 7% wt. to about 9% wt. hydrogen, from about 8% wt. to about10% wt. hydrogen, from about 9% wt. to about 11% wt. hydrogen, fromabout 10% wt. to about 12% wt. hydrogen, from about 11% wt. to about 13%wt. hydrogen, from about 12% wt. to about 14% wt. hydrogen, from about13% wt. to about 15% wt. hydrogen, from about 14% wt. to about 16% wt.hydrogen, from about 15% wt. to about 17% wt. hydrogen, from about 16%wt. to about 18% wt. hydrogen, from about 17% wt. to about 19% wt.hydrogen, and from about 18% wt. to about 20% wt. hydrogen.

The solid fuel composition may include from about 5% wt. to about 20%wt. oxygen. The solid fuel composition may include from about 5% wt. toabout 7% wt. oxygen, from about 6% wt. to about 8% wt. oxygen, fromabout 7% wt. to about 9% wt. oxygen, from about 8% wt. to about 10% wt.oxygen, from about 9% wt. to about 11% wt. oxygen, from about 10% wt. toabout 12% wt. oxygen, from about 11% wt. to about 13% wt. oxygen, fromabout 12% wt. to about 14% wt. oxygen, from about 13% wt. to about 15%wt. oxygen, from about 14 wt. to about 16% wt. oxygen, from about 15%wt. to about 17% wt. oxygen, from about 16% wt. to about 18% wt. oxygen,from about 17% wt. to about 19% wt. oxygen, and from about 18% wt. toabout 20% wt. oxygen.

The solid fuel composition may include less than about 2% wt. sulfur.The solid fuel composition may include less than about 1% wt. sulfur,less than about 0.5% wt. sulfur, and less than about 0.1% wt. sulfur.

The solid fuel composition may include less than about 2% wt. chlorine.The solid fuel composition may include less than about 1% wt. chlorine,less than about 0.5% wt. chlorine, and less than about 0.1% wt.chlorine.

The solid fuel composition may include less than about 2% wt. water. Thesolid fuel composition may include less than about 1% wt. water, lessthan about 0.5% wt. water, and less than about 0.1% wt. water. The solidfuel composition may include less than about 1% wt. water.

The solid fuel composition, when burned, may release significantly lowerlevels of toxins when burned compared to unprocessed solid waste. Theamount of toxins released can and will vary. The solid fuel compositionmay release less than about 0.5 lb. alkali oxide, less than about 3 lb.ash, less than about 0.1 lb. sulfur dioxide (SO₂), and less than about1.5 lb. of chlorine per million BTU when burned. The solid fuelcomposition may release less than about 0.5 lb. alkali oxide per millionBTU when burned. The solid fuel composition may release less than about3 lb. ash per million BTU when burned. The solid fuel composition mayrelease less than about 0.1 lb. sulfur dioxide (SO₂) per million BTUwhen burned. The solid fuel composition may release less than about 1.5lb. of chlorine per million BTU when burned.

The solid fuel composition may release an amount of ash ranging frombetween about 1 lb. and about 30 lb. per million BTU when burned, suchas between about 1 lb. and 2 lb., between about 2 lb. and 3 lb., betweenabout 3 lb. and 4 lb., between about 4 lb. and 5 lb., between about 5lb. and 10 lb., between about 10 lb. and 15 lb., between about 15 lb.and 20 lb., between about 20 lb. and 25 lb., or between about 25 lb. and30 lb.

The solid fuel compositions may be used as an engineered feedstock toreplace or supplement coal, biomass or other alternative fuels during anincarnation, pyrolysis or gasification process.

EXAMPLE

Ten tons of municipal solid waste is delivered. The MSW has a watercontent of about 20% wt. to about 40% wt. and comprises a variety ofresidential and commercial solid wastes, including an unknown amount ofnon-combustible solid waste and mixed plastics content. The MSW isscreened for non-combustible solid waste. The non-combustible solidwaste, including any glass, metal, bricks and stones, is removed. TheMSW is then analyzed for its mixed plastics content. The amount of mixedplastics in the MSW is adjusted to between about 5% wt. and about 60%wt. Once the non-combustible solid waste is removed and the mixedplastics content is adjusted, the MSW is shredded to an average particlesize equal to or less than other individual pieces within the MSW.

The shredded MSW is introduced into a process vessel as describedherein. The MSW is heated to a temperature between about 90° C. andabout 110° C. while mixing. This process separates the MSW into driedMSW and vaporized compounds, which include mostly water vapor and somevolatile organic compounds that have a boiling point below about 110° C.The temperature of the MSW is maintained below about 110° C. so that themixed plastics do not prematurely melt and trap water.

The vaporized compounds are removed from the process vessel by reducingthe pressure within the process vessel to less than about 50 torr usinga vacuum system attached at the vacuum port. A condenser between theprocess vessel and the vacuum pump of the vacuum system traps thevaporized compounds by condensing them into wastewater.

Within the process vessel, mixing continues while the vaporizedcompounds are removed under reduced pressure. The heat is then increasedto between about 190° C. and about 260° C., melting the plastics withinthe dried MSW. The oil used to heat the walls of the process vessel canbe up to 30° C. hotter than the interior volume of the process vessel,because the constant mixing evenly distributes heat throughout the MSW.The mixing process also further homogenizes the MSW. The temperature andpressure conditions are also sufficient to liberate further water notevaporated in the drying step and to liberate other VOCs. Moreover,these process conditions vaporize chlorinated organic compounds andchlorine gas derived primarily from chlorine containing plastics in theMSW, such as polyvinylchloride (PVC) and polyvinylidene chloride, Thesechlorinated organic compounds and chlorine gas also condense in thecondenser, joining the wastewater there.

While still hot, but not above 200° C., the dried MSW containing moltenmixed plastics is extruded through the extrusion outlet. As the MSW isextruded, it is cut into 2-inch long chucks. The extruded MSW is placedon a water-cooled conveyor where it is cooled to less than about 65° C.,forming a solid fuel composition.

Based upon calorimetric analysis and density measurement, the solid fuelcomposition has an energy content of about 13,000 BTU/lb., and a densityranging of about 50 lb./ft³. Elemental analysis indicates that theresulting solid fuel has from about 60% wt. carbon, about 10% wt.hydrogen, about 10% wt. oxygen, less than about 2% wt. sulfur, less thanabout 2% wt. chlorine, and less than about 1% wt. water.

No syngas is formed during the process. The observed vaporized compoundsare not the result of pyrolysis or gasification. Thus, the resultingsolid fuel composition is not pyrolyzed.

The foregoing merely illustrates the principles of the invention.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.It will thus be appreciated that those skilled in the art will be ableto devise numerous systems, arrangements and methods which, although notexplicitly shown or described herein, embody the principles of theinvention and are thus within the spirit and scope of the presentinvention. From the above description and drawings, it will beunderstood by those of ordinary skill in the art that the particularembodiments shown and described are for purposes of illustrations onlyand are not intended to limit the scope of the present invention.References to details of particular embodiments are not intended tolimit the scope of the invention.

What is claimed is:
 1. A method comprising: heating, in a processvessel, a solid waste composition comprising one or more plastics in atotal amount of about 5 wt. % to about 60 wt. % of the solid wastecomposition; drying, in the process vessel, the solid waste compositionto form a dried solid waste mixture having water in an amount of lessthan 2 wt. % of the dried solid waste mixture; melting, in the processvessel, at least a portion of the one or more plastics of the driedsolid waste mixture at below atmospheric pressure; and forming a solidfuel composition from the dried solid waste mixture, the solid fuelcomposition having an energy content of at least about 8,000 BTU/lb. 2.The method of claim 1, further comprising vaporizing compounds from thesolid waste composition, wherein the vaporized compounds comprise watervapor, volatile organic compounds, chlorinated organic compounds,chlorine gas, or any combination thereof.
 3. The method of claim 2,further comprising separating the vaporized compounds from the driedsolid waste mixture in the process vessel.
 4. The method of claim 3,further comprising removing the vaporized compounds via a vacuum port ofa vacuum pump from the process vessel.
 5. The method of claim 1,wherein, following the melting, forming the solid fuel compositioncomprises extruding at least a portion of the dried solid waste mixtureto yield an extrudate.
 6. The method of claim 5, further comprisingcooling the extrudate to yield the solid fuel composition.
 7. The methodof claim 1, wherein the solid waste composition comprises municipalsolid waste and agricultural waste.
 8. The method of claim 1, furthercomprising analyzing the solid waste composition for non-combustiblecomponents and, when present, removing the non-combustible components.9. The method of claim 1, further comprising analyzing the solid wastecomposition for content of the one or more plastics and adjusting atotal amount of the one or more plastics in the solid waste compositionto between about 5 wt. % and about 60 wt. %.
 10. The method of claim 1,wherein the one or more plastics comprise one or more of polyester,polyethylene terephthalate, polyethylene, polyvinyl chloride,polyvinylidene chloride, polypropylene, polystyrene, polyamides,acrylonitrile-butadiene-styrene,polyethylene/acrylonitrile-butadiene-styrene, polycarbonate,polycarbonate/acrylonitrile butadiene styrene, polyurethanes,maleimide/bismaleimide, melamine formaldehyde, phenol formaldehydes,polyepoxide, polyetheretherketone, polyetherimide, polyimide, polylacticacid, polymethylmethacrylate, polytetrafluoroethylene, andurea-formaldehyde.
 11. The method of claim 1, wherein the solid wastecomposition comprises from about 5 wt. % to about 35 wt. % of a totalamount of the one or more plastics.
 12. The method of claim 1, whereinthe solid fuel composition comprises: from about 40 wt. % to about 80wt. % carbon; from about 5 wt. % to about 20 wt. % hydrogen; oxygen;less than about 2 wt. % sulfur; and less than about 2 wt. % chlorine.13. The method of claim 1, further comprising shredding the solid wastecomposition into pieces having a maximum dimension or maximum diameterof about two inches prior to heating the solid waste composition in theprocess vessel.
 14. The method of claim 1, further comprising contactingthe solid waste composition with a surface in the process vessel havinga temperature of at least 190° C.
 15. The method of claim 14, furthercomprising contacting the solid waste composition with a surface in theprocess vessel having a temperature in a range from about 190° C. toabout 280° C.
 16. The method of claim 1, further comprising heating thesolid waste composition in the process vessel to a temperature of atleast 160° C.
 17. The method of claim 16, further comprising heating thesolid waste composition in the process vessel to a temperature in arange from about 160° C. to about 250° C.